Briggs & Stratton 44S977-0016-G1 Vertical Professional Series OHV Engine, 724cc, 25.0 Gross HP, 1″ x 3-5/32″ Crankshaft, 1/4″ Square Keyway, 7/16″-20 Drilled & Tapped, 12 Volt Gear Drive Starter, Suppress Afterfire Solenoid, 16 Amp DC Alternator